1. Field of the Invention
The present invention relates to an optical sensor for sensing peripheral light and a liquid crystal display device using the same, and more particularly to an optical sensor providing enhanced reliability in sensing peripheral light and reduced power consumption, and a liquid crystal display device incorporating this optical sensor.
2. Discussion of the Related Art
Recently, various flat panel displays capable of reducing weight and volume that are intrinsic disadvantages of cathode ray tubes (CRT) have been developed. Flat panel displays include liquid crystal displays (LCD), field emission displays (FED), plasma display panels (PDP), and organic light emitting displays.
LCDs have advantages such as small-size, light-weight and low-power; they have come into the spotlight as a substitute for a CRT, and may eliminate the intrinsic disadvantages of the CRT. Recently, the LCD has been mounted in portable devices such as a portable phone, a private digital assistor (PDA), a monitor, and a television. The LCD, which is a transmissive display device, displays a desired image by adjusting the amount of light transmitted through a liquid crystal layer according to anisotropic refractive indexes of liquid crystal molecules in the liquid crystal layer.
A contemporary active matrix type LCD is typically constructed with a pixel region, a scan driver, a data driver, a gamma voltage supply section, a timing controller, and a backlight driver.
Inside the pixel region, m×n liquid crystal cells are arranged in a matrix pattern, and m data lines intersect n scan lines. A thin film transistor is formed at the intersections of the data lines and the scan lines. The scan driver supplies a scan signal to the scan lines. The data driver supplies a data signal to the data lines. The gamma voltage supply section supplies a gamma voltage to the data driver. The timing controller supplies control signals to the scan driver and the data driver. The backlight driver drives a backlight, which supplies light to the liquid crystal cells.
In the aforementioned LCD, the backlight always irradiates light of a constant brightness to the pixel region. In case that an ambient environment becomes darker, although it is not necessary for great amount of light, the backlight, however, supplies light of a constant brightness to the pixel region. This increases power consumption of the backlight. In practice, the backlight undesirably consumes more than 80% of the power necessary to drive the LCD. Therefore, in order to reduce the power consumption, it is necessary to reliably sense peripheral light and reduce the amount of light generated by the backlight when the peripheral light is less than the brightness necessary to conform to the ambient peripheral light.